A semiconductor device in operation generates heat which must be dissipated in order to prevent damage to the device. Generally, the heat is dissipated by means of a heat sink. The heat sink must be attached to the semiconductor device so that thermal resistivity between the heat sink and the device is minimized, and this condition must be maintained despite vibration and shock to the assembly. The heat sink should also be attached removably so that the chip carrier package may be replaced or the substrate repaired, if necessary. It is a problem to attach heat sinks to semiconductor devices quickly, simply and removably without damaging the fragile ceramic packages which contain the semiconductor chips.
One technique for attaching a heat sink to a semiconductor device is the stud and nut approach where a slug is brazed to the back of a ceramic chip carrier and two threaded studs are brazed onto the slug. The heat sink, which has holes drilled into it, is inserted over the studs and fastened down with nuts. This method is expensive because of the number and complexity of pieces involved. This method is also time-consuming to assemble because of the number of steps involved and the time needed to align the heat sink on the stud and to tighten the nut down.
In another method for attaching a heat sink, a plastic frame has openings to accept pins of the chip carrier, and a spring clips around the frame to hold the heat sink onto the chip carrier, as shown for example in U.S. Pat. No. 4,716,494, issued to E. J. Bright, et al. on Dec. 29, 1987.
A further example of a heat sink attachment method is to first place a plastic frame between the chip and the board, then insert the chip carrier and then snap a spring over the frame. Such a method is shown in U.S. Pat. No. 4,745,456 issued to D. L. Clemens on May 17, 1988.
It remains desirable to find a quick and simple method for attaching a heat sink to a chip carrier that maintains good thermal contact, does not damage the chip carrier and may be assembled or disassembled at any time.